The present invention relates to a fuel system for an internal combustion engine and, particularly, to a method and an evaporation emissions canister which includes an integral liquid fuel trap for improved separation of liquid fuel which is entrained along with the fuel vapor from the fuel tank to the evaporative emissions canister in the fuel system.
Presently, fuel systems employed in the automotive industry contain an evaporative emissions canister to control evaporative emissions from the automotive fuel tank. Examples of evaporative emissions canisters are described in U.S. Pat. No. 4,203,401 to Kingsley et al.; U.S. Pat. No. 4,658,796 TO Yoshida et al.; U.S. Pat. No. 4,683,862 to Fornuto et al.; U.S. Pat. No. 5,119,791 to Gifford, et to Cotton; U.S. Pat. No. 5,924,410 to Dumas et al.; U.S. Pat. No. 5,957,114 to Johnson et al; U.S. Pat. No. 6,136,075 to Bragg et al; U.S. Pat. No. 6,237,574 to Jamrog et al.; and RE38, 844 to Hiltzik et al.
Typically, the evaporative emissions canisters include an adsorbent material such as activated carbon to adsorb the fuel vapors emitted from the fuel tank. The carbon filled canister adsorbs the fuel vapor until it becomes saturated, at which time, fresh air drawn through the canister removes the fuel vapor therefrom and sends it to the engine by means of suitable conduits and flow control devices. Such fuel systems not only permit the vapor to flow to the canister but also have the potential to allow liquid fuel entrained with the fuel vapor to travel from the fuel tank to the canister where it saturates at least a portion of the adsorbent carbon bed causing the carbon to become non-functional until the liquid is evaporated and purged from the carbon bed. This decreases the overall working capacity of the adsorbent material and the efficiency of the canister resulting in possible emissions to the atmosphere. To prevent this, some fuel systems incorporate a device inside the fuel tank where the liquid fuel is trapped and returned to the tank. Such devices are not entirely satisfactory since small amounts of liquid fuel are entrained with the fuel vapor and enter the emissions canister where it has the potential to reduce the effectiveness of the emissions canister. Emissions canisters have been provided with a liquid fuel trap, which is designed to allow the liquid fuel to enter the canister but will not allow it to enter the adsorbent material bed. Once the liquid enters the liquid fuel trap it simply sits there until it either evaporates on its own due to the properties of the gasoline or it will be drawn out of the canister during the purge cycle of the vehicle and conveyed back to the engine where it is consumed. However, such canisters generally require that an additional welding step be performed in the manufacture of the canister/liquid fuel trap system, wherein a seal is created between the fuel trap and the canister. Typically, the fuel trap is installed into the canister via a plastic welding process such as vibration welding, ultrasonic welding, etc. The manufacture of such evaporative emissions canisters is both time consuming and economically unattractive.
Typically, evaporative emissions canisters with incorporated liquid fuel traps have been manufactured by mounting the liquid fuel trap into of the canister, providing a basin for any invasive liquid fuel. For example, U.S. Pat. No. 5,119,791 to Gifford, et al. specifically teaches the use of a liquid trap with a vapor storage canister wherein the liquid-fuel trap consists of a cup that forms an interior cavity at the bottom of, and surrounded by, the carbon adsorbent bed. The fuel vapor with entrained liquid fuel emitted from the fuel tank is directed to the liquid-fuel trap through a fill tube. The liquid fuel settles out in the cup where it remains until it is later vaporized. The fuel vapor enters the carbon bed through a grid. During purge, vacuum is applied to a central purge tube that extends all the way through the carbon bed and cup into a plenum located below the cup. It is apparent from the above that there exists a need in the art for an automotive evaporative emissions canister which effectively prevents liquid fuel from entering and saturating the carbon bed in the canister, and which also eliminates the requirement for an additional sealing step between the fuel separator and the canister in the manufacturing process. Furthermore, it is desirable to provide an evaporative emissions canister having a simple construction, which does not require the insertion of the associated tubes all the way into the chambers of the evaporative emissions canister.